Historically, only two methods for serological detection of HLA specificities have been popularly used since the introduction of routine tissue typing almost two decades ago. The first of these, a leukoagglutination technique, was replaced during the late 1960s by more sensitive and reliable cytotoxicity assays which were developed on a micro-scale by Kissmeyer-Nielson and by Terasaki, P. I. and McClelland, J. D.; Microdroplet assay for human serum cytotoxins, Nature, 206:998-1000 (1964). Microcytotoxicity remains standard today as it enables the simultaneous assessment of the reaction of a patient's cells with a very large number of scarce HLA typing sera which can be used in minute quantities.
Since the description of the close association of HLA-B27 with AS, a significant proportion of the labors of tissue-typing laboratories has been directed at assessment of HLA-B27 status, irrespective of the patient's full HLA phenotype. Requests for B27-typing by rheumatologists and other physicians have grown steadily despite frequent warnings that B27-status should rarely, if ever, be used as a diagnostic criterion for AS, as 8% of the (Caucasian) population is HLA-B27.sup.+ and only a small minority of these ever develop AS. At Royal Melbourne Hospital, for example, 45% of the 2500 requests for tissue typing during 1983 were solely for B27 status. Thus far, B27-typing has always been performed along routine tissue-typing lines, testing a panel of anti-B27 sera on the patient's lymphoctyes, and this has proven costly in terms of materials (especially antisera) and particularly because of recently escalating labor costs.
The aim of a full panel of standardized monoclonal HLA-typing sera is still a distant one, however, monoclonal antibodies may have much to offer in certain specific situations such as B27-typing. Accordingly, a number of procedures which have utilized an anti-HLA-B27 monoclonal antibody, have been developed, which should enable rapid, cheap and dependable assessment of B27 status. It is contended that these techniques will lead to a marked reduction in the costs of HLA-B27 typing, both in terms of staff labour and the costs of disposable reagents, allowing the direction of these resources to other services.